Abstract
BackgroundAqueous zanamivir solution, an investigational product, was provided by the manufacturer on compassionate grounds for parenteral administration to severe H1N1pdm09 influenza cases during the 2009 pandemic.ObjectiveTo describe characteristics and outcomes of UK patients receiving parenteral zanamivir therapy.MethodsCollaborators at multiple hospital sites gathered retrospective data on patients receiving aqueous zanamivir therapy between Q4 2009 and Q1 2011. We present analysis of the demographics, clinical features, treatment and outcomes of this cohort.ResultsData on 185 cases were obtained (response rate of 38%; median age 43 years; 62% male; 17% non‐Caucasian ethnic group). Most frequent co‐morbidities included cancer, immunosuppression and respiratory conditions. Most patients received intravenous zanamivir alone (90%), for durations of up to 21 days. 13% of cases had adverse effects related to zanamivir therapy. Thirty four percentage of cases died. No significant relationship was seen between mortality and timing or route of administration of aqueous zanamivir therapy.ConclusionsThe response rate of this observational study of the outcomes of treatment of severe influenza was low, allowing limited conclusions to be drawn. Some potential adverse effects were noted. Clinicians should carefully consider potential risks and benefits of use of this product. New treatment options are urgently required to improve outcomes for patients with severe influenza infections.
Highlights
Most cases of pandemic H1N1pdm[09] influenza experienced uncomplicated illness or asymptomatic infection.[1]
We summarised the characteristics of cases treated with parenteral zanamivir aqueous solution in terms of demographics; co- morbidities, pregnancy and body weight; influenza vaccination status; clinical and radiographic findings; prior antiviral therapy; timing, route and duration of aqueous zanamivir administration; other medical treatment and respiratory support; complications and co-infections; reported adverse events; length of stay and mortality
Median overall Sequential Organ Failure Assessment (SOFA) scores were higher for cases given intravenous aqueous zanamivir therapy (10, vs 4 and 5 for cases treated with nebulised therapy or via both routes respectively; P = 0.0005 by Kruskal-Wallis test)
Summary
Most cases of pandemic H1N1pdm[09] influenza experienced uncomplicated illness or asymptomatic infection.[1] A minority of severe cases developed acute respiratory distress syndrome (ARDS) requiring respiratory support. Two neuraminidase inhibitors were licensed for influenza in the United Kingdom at the time. Oseltamivir may be administered orally and is well absorbed.[2] Zanamivir may be. Administered by powder inhaler.[3] Nebulised administration of zanamivir inhalation powder as a liquid formulation is not recommended.[4] Few alternative antiviral formulations were available for critically ill patients with oseltamivir-resistant infections, impaired gastric motility, malabsorption and/or gastrointestinal bleeding
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